Preassembly of a camshaft phaser

ABSTRACT

A camshaft phasing system ( 10 ) for an internal combustion engine ( 6 ) includes a camshaft ( 16 ) and a camshaft phaser ( 15 ) that is axially slid onto the camshaft ( 16 ) and that has stator ( 34 ) and a rotor ( 36 ) driven by the stator ( 34 ), whereby the rotor ( 36 ) is mounted rotatably relative to the stator ( 34 ). A bushing ( 26 ) that is secured on the camshaft ( 16 ) is provided, whereby the camshaft phaser ( 15 ) is tightened on the camshaft ( 16 ) against the bushing ( 26 ). Moreover, a drive has an internal combustion engine and such a camshaft phasing system.

The invention relates to a camshaft phasing system and it also relatesto a drive with the camshaft phasing system.

BACKGROUND OF THE INVENTION

German patent application DE 10 2009 041 873 A1 discloses a camshaftphasing system in which a camshaft is rotatably connected via its endface to a camshaft phaser. The camshaft phaser can influence the timingof the transmission of drive power to the camshaft, for example, inorder to change the valve timing in an internal combustion engine.

SUMMARY OF THE INVENTION

It is an object of the present invention to improve upon a prior-artcamshaft phasing system.

In a prior-art camshaft phasing system, the camshaft phaser has to bemounted concentrically on the camshaft in order to avoid unbalances thatcan lead to noisy vibrations and to greater wear and tear of theprior-art camshaft phasing system.

In the prior-art camshaft phasing system, a concentric mounting of thecamshaft phaser on the camshaft is labor-intensive. In addition, narrowmanufacturing tolerances have to be observed. The camshaft phasingsystem should only be assembled when it is being installed in theinternal combustion engine. However, this not only leads to undesiredhigher costs for the manufacturer of the internal combustion engine butthere is also fundamentally the risk of improper assembly of thecamshaft phasing system in the internal combustion engine.

The present invention provides sliding the camshaft phaser axially ontothe camshaft and tightening it on the camshaft against a bushing. Thepartial axial placement of the camshaft in the camshaft phasersimplifies the assembly of the camshaft phaser on the camshaft. In theassembled state, a sturdy concentric connection is created between thecamshaft phaser and the camshaft. Through the tightening of the camshaftphaser on the camshaft, the camshaft phaser is mounted radially andnon-rotatably on the camshaft, whereby a torque is transmitted from thecamshaft phaser to the camshaft via the bushing. The radial mounting ofthe camshaft phaser onto the camshaft translates into aneasy-to-assemble camshaft phasing system with a secure concentricconnection of the camshaft phaser to the camshaft. Such a camshaftphasing system can be prefabricated by its manufacturer, whereas itsfinal assembly as a system is carried out by the manufacturer of theinternal combustion engine. Since the camshaft phaser is radiallymounted on the camshaft and axially slid into place, the inventioncreates additional ways to simplify the assembly such as, for example,by using axial guide mechanisms such as teeth or the like.

The invention also simplifies the installation of the camshaft phasingsystem since, in order to install the camshaft phasing system, it ismerely necessary to assemble the entire system without the risk thatparts which might be forgotten during the installation would then stillhave to be delivered, entailing considerable costs.

The bushing can be configured in any desired manner. For example, thebushing can be ring-shaped or else it can form just a partial ring. Itis also possible for the bushing to have steps or the like. The bushingprovides a ring-shaped or partially ring-shaped stop surface on thecamshaft for the camshaft phaser and, via this stop surface, thecamshaft phaser can be joined to the bushing and thus mounted axiallyand non-rotatably on the camshaft. The size of the stop surface can bespecified as desired as a function of the wall thickness of the bushing.Consequently, the non-rotatable mounting of the camshaft phaser on thecamshaft can be ensured as a function of the wall thickness of thebushing so that the anticipated torques can be reliably transmitted. Aseparate bushing offers the additional advantage that a material that isoptimized for the non-rotatable, frictional connection of the camshaftphaser can be selected independently of the material of the camshaft.

Therefore, the invention puts forward a camshaft phasing system for aninternal combustion engine that comprises a camshaft as well as acamshaft phaser that is slid axially onto the camshaft and that hasstator and a rotor driven by the stator, whereby the rotor is mountedrotatably relative to the stator. According to the invention, thecamshaft phasing system has a bushing that is secured on the camshaft,whereby the camshaft phaser is tightened on the camshaft against thebushing.

The separate bushing can fundamentally be secured in any desired manner.A positive connection such as, for instance, a screwed connection or asliding block connection, is likewise possible, and so is a frictionalconnection with which a friction-increasing means is inserted betweenthe camshaft and the bushing.

In a special refinement, the bushing is held on the camshaft via a pressfit. The press fit is especially advantageous since it acts along thecircumference of the camshaft and thus distributes the mechanical loadswhile the torque is being transmitted from the camshaft phaser onto thecamshaft uniformly along the circumference of the camshaft. The assemblyof the bushing is also quite simple.

In one refinement, the rotor is tightened on the camshaft against thebushing. In this manner, the stator can take up the drive power for thecamshaft and transmit it via the rotor to the camshaft in aphase-shifted manner.

In another refinement, the camshaft has an axial stop for the bushing onwhich the bushing can be mounted on a counter-bearing in order totighten the camshaft phaser. In this manner, it is not only possible toincrease the tightening effect of the bushing, but also, the axial stopsimultaneously serves as a positioning element that prescribes theposition of the bushing on the camshaft.

In a preferred refinement, the camshaft phasing system has a nut fortightening the camshaft phaser, especially the rotor, against thebushing. Owing to the torque while the nut is being screwed in, thetightening forces can be set, on the one hand, in order to protect thecamshaft phasing system against an excessive tightening stress and, onthe other hand, to ensure sufficient tightening so that the camshaftphaser is mounted non-rotatably and radially on the camshaft.

In another preferred embodiment, the camshaft phaser, especially therotor, is frictionally connected to the bushing. A friction couplingbetween the bushing and the camshaft phaser, especially the bushing,allows a simple assembly, since the friction partners are pressed flatagainst each other. By means of suitable material pairing, the normalforce can optionally be reduced, so that smaller tightening forces areneeded. Especially preferably, a diamond perforated disk is placedbetween the camshaft phaser or the rotor and the bushing, whereby thisdiamond perforated disk creates an adequate frictional connection, evenwhen the normal force is reduced. As a result, the torques that can betransmitted via the bushing from the camshaft phaser to the camshaft canbe increased. As an alternative or additionally, a non-rotatableconnection can also be achieved by means of a positive or adhesiveconnection.

In another embodiment of the invention, the camshaft phasing system hasan outer tubular camshaft in which the camshaft is held concentrically,whereby the outer camshaft is connected to the stator of the camshaftphaser. Owing to the outer camshaft, a double camshaft phasing systemhaving only a single camshaft phaser can be put forward that is able toactuate the inlet valves and the outlet valves of an internal combustionengine independently of each other.

In a special embodiment, the outer camshaft and the stator of thecamshaft phaser are positively connected, especially by teeth. Thanks toa tangential positive connection of the type achieved, for instance, byteeth, the stator can rotate the outer camshaft relative to the innercamshaft, but it can move axially on the outer camshaft. This axialmovement capability achieves a further simplification of the assemblysince the camshaft phaser can be slid over the stator axially onto theouter camshaft, whereby especially the teeth serve as a guiding aid. Theteeth or the tangential positive connection also function as anon-rotatable radial bearing.

In an especially preferred embodiment, the stator is additionallymounted radially on the bushing. This, too, translates into a simplifiedassembly. The camshaft phaser is additionally positioned opposite to thecamshaft.

The invention also puts forward a drive comprising an internalcombustion engine having a driven shaft, and a camshaft phasing systemas described above for actuating a valve of the internal combustionengine based on a rotation of the driven shaft.

BRIEF DESCRIPTION OF THE DRAWING

An embodiment of the invention will be described in greater detail belowwith reference to a drawing.

The FIGURE shows a drive system according to one embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE DRAWING

The single FIGURE shows a drive system 2 in which valves 4 of aschematically depicted internal combustion engine 6 are actuated by adouble camshaft 8 of a camshaft phasing system 10. The internalcombustion engine 6 drives a driven shaft 12 that drives a camshaftphaser 15 via an endless drive 14 in a manner still to be described. TheFIGURE shows the endless drive 14 in the open position.

The double camshaft 8 has an inner camshaft 16 that is heldconcentrically in an outer camshaft 18. On each of the camshafts 16, 18,there are corresponding cams 20, 22 that, for the sake of clarity, areshown in a synchronous position in the FIGURE. During actual use, thecam 20 of the inner camshaft 16 is angle-offset relative to the cam 22of the outer camshaft 18.

The inner camshaft 16 runs concentrically and rotatably in the outercamshaft 18. Via an axial seal 24, it is axially secured in the outercamshaft 18. The axial seal 24 can be formed, for example, by a groovethat extends around the inner camshaft 16 and by a groove (without areference numeral) into which a projection (without a reference numeral)protruding from the inside of the outer camshaft 18 enters.

The camshaft phaser 15 is slid concentrically onto the inner camshaft 16and onto the outer camshaft 18, and it is tightened against the innercamshaft 16 between a bushing 26 and a nut 28. Here, the bushing 26 isaxially mounted on a counter-bearing at an axial stop 30 on the innercamshaft 16. The nut 28 is screwed onto an axial end section 32 of thecamshaft 16. In this embodiment, the tightening force needed to hold thecamshaft phaser 15 is generated by screwing the nut 28 onto the axialend section 32 and by the axial mounting of the bushing 26 on acounter-bearing against the axial stop 30.

The camshaft phaser 15 has a stator 34 and a rotor 36 whose phase shiftscan be adjusted relative to each other in a manner known to the personskilled in the art. Whereas the stator 34 is rotatably connected to theouter camshaft 18, the rotor 36 is non-rotatably connected to the innercamshaft 16.

The non-rotatable connection between the stator 34 and the outercamshaft 16 is established by teeth. 38. In addition, the stator 34 ismounted radially on the bushing 26. Both of these measures permit asimple and less error-prone assembly of the camshaft phaser 15 on thecamshaft 16, 18.

The non-rotatable connection between the rotor 36 and the inner camshaft16 is created by means of tightening with the nut 38 and the bushing 26,whereby the bushing 26 is non-rotatably connected to the inner camshaft16 via a press fit. A diamond ring 40 between the rotor 36 and thebushing 26 further improves the frictional and thus non-rotatableconnection.

The stator 34 has a hub 42 that is connected via the teeth 38 to theouter camshaft 18. A drive wheel is formed in one piece with the hub 42,and the endless drive 14 is wrapped around this drive wheel so that thestator 34 can drive the outer camshaft 18 via the driven shaft 12, andthe rotor 36 can drive the inner camshaft 16 via the stator 34. On theside of the hub 42 opposite from the outer camshaft 18, there is anadjoining stator housing 44 in which the rotor 36 is accommodated. Thestator housing 44 is closed by a cover 46 that is affixed to the housing44 by means of pins 48 that have been screwed into the hub 42.

LIST OF REFERENCE NUMERALS

-   2 drive means-   4 valves-   6 internal combustion engine-   8 double camshaft-   10 camshaft phasing system-   12 driven shaft-   14 endless drive-   15 camshaft phaser-   16 inner camshaft-   18 outer camshaft-   20 cam-   22 cam-   24 axial seal-   26 ushing-   28 nut-   30 axial stop-   32 axial end section-   34 stator-   36 rotor-   38 teeth-   40 diamond disk-   42 hub-   44 stator housing-   46 cover-   48 pins

What is claimed is: 1-10. (canceled)
 11. A camshaft phasing system foran internal combustion engine, the camshaft phasing system comprising: acamshaft; a camshaft phaser axially slid onto the camshaft and havingstator and a rotor driven by the stator, the rotor being mountedrotatably relative to the stator; and a bushing secured on the camshaft,the camshaft phaser tightened on the camshaft against the bushing. 12.The camshaft phasing system as recited in claim 11 wherein the rotor istightened on the camshaft against the bushing.
 13. The camshaft phasingsystem as recited in claim 11 wherein the bushing is held on thecamshaft via a press fit.
 14. The camshaft phasing system as recited inclaim 11 wherein the camshaft has an axial stop for the bushing.
 15. Thecamshaft phasing system as recited in claim 11 further comprising a nutfor tightening the camshaft phaser against the bushing.
 16. The camshaftphasing system as recited in claim 15 wherein the nut tightens therotor.
 17. The camshaft phasing system as recited in claim 11 whereinthe stator is mounted radially on the bushing.
 18. The camshaft phasingsystem as recited in claim 11 wherein the camshaft phaser isfrictionally connected to the bushing.
 19. The camshaft phasing systemas recited in claim 18 wherein the rotor is frictionally connected tothe bushing.
 20. The camshaft phasing system as recited in claim 11further comprising an outer tubular camshaft, the camshaft being heldconcentrically in the outer tubular camshaft, the outer tubular camshaftbeing connected to the stator of the camshaft phaser.
 21. The camshaftphasing system as recited in claim 20 wherein the outer tubular camshaftand the stator of the camshaft phaser are positively connected.
 22. Thecamshaft phasing system as recited in claim 21 wherein teeth positivelyconnect the outer tubular camshaft and the stator.
 23. A drivecomprising: an internal combustion engine having a driven shaft; and